None.
The present invention generally relates to a rotary die curl assembly for forming container end panels, commonly called shells, from a sheet of material. More particularly, the present invention relates to a rotary die curl assembly capable of curling and reforming an end in a single rotary press.
The forming of ends or shells for containers is well-known in the art. Representative patents disclosing end forming include Bulso U.S. Pat. Nos. 4,516,420 and 4,549,424. Similarly, devices have been developed to perform reforming and curling operations. Representative examples of these operations may be found in Bulso U.S. Pat. Nos. 4,587,825 and 4,574,608. At least one device has combined the curling and reforming steps in a single press. But, in that device, the end must travel to separate curling and reforming stations. The necessity of having multiple stations increases the size and complexity of the machine. Consequently, a need has existed in the art for a press that can combine the curling and forming or reforming steps in a single station.
Accordingly, an object of the present invention is to combine the reforming and curling steps in a single rotary die curl assembly.
It is also an object of the present invention to provide means for compensating for the thermal expansion of the press during operation.
In light of at least one of the foregoing objects, the present invention provides a rotary die curl assembly including a punch assembly and a die assembly axially aligned and selectively engageable with each other. The punch assembly includes a punch holder mounted on a punch center post. The punch holder haves an annular end that extends toward the die assembly where the end has an axially inward and radially inward extending tips. A curling punch is received within the punch holder. A punch core mounted within the curling punch and includes an axially extending periphery located adjacent to the curling punch and defining a recess therebetween. The curling punch extends axially outward of said punch holder and said punch core. The die assembly includes a curling die received within a die holder and defining a bore. A lower pressure is mounted within the bore and slideable relative to the curling die. A die core is located within the lower pressure pad and has a raised edge located beneath the recess in said punch assembly. An upper spring holder is located below the curling die, the lower pressure pad, and the die core supporting at least one of the curling die, lower pressure pad and die core, and a lower spring holder is located below the upper spring holder and held in spaced relation therefrom by a spacing assembly defining a gap between said upper spring holder and said lower spring holder whereby thermal expansion of either of the punch assembly or die assembly is compensated for by the spacing assembly and the gap.
The present invention further provides an apparatus for forming container shells from material fed into a press, including at a single station, tooling for curling the shell and tooling for forming or reforming the shell including a punch assembly and a die assembly carried by the press adapted to curl and form or reform the shell in a single stroke.